U.S. patent application number 09/997822 was filed with the patent office on 2002-06-06 for composite membranes and methods for making such membranes.
Invention is credited to Boggs, Daniel R., McLarty, Donna L., Pauley, Robin G., Sternberg, Shmuel.
Application Number | 20020066699 09/997822 |
Document ID | / |
Family ID | 22341116 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020066699 |
Kind Code |
A1 |
Boggs, Daniel R. ; et
al. |
June 6, 2002 |
Composite membranes and methods for making such membranes
Abstract
Membranes and methods for making membranes are disclosed. The
membranes include a polymeric matrix and a particulate material
immobilized within the matrix. The membranes may find particular
application in methods and apparatus for removing organic compounds
from a biological fluid as part of a pathogen inactivation
treatment.
Inventors: |
Boggs, Daniel R.;
(Libertyville, IL) ; Sternberg, Shmuel; (Palatine,
IL) ; Pauley, Robin G.; (Lake Villa, IL) ;
McLarty, Donna L.; (Hoffman Estates, IL) |
Correspondence
Address: |
Michael C. Mayo
Baxter Healthcare Corporation
Fenwal Division, RLP-30
P.O. Box 490 - Route 120 & Wilson Road
Round Lake
IL
60073
US
|
Family ID: |
22341116 |
Appl. No.: |
09/997822 |
Filed: |
November 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09997822 |
Nov 30, 2001 |
|
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|
09111915 |
Jul 8, 1998 |
|
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Current U.S.
Class: |
210/483 ;
210/488 |
Current CPC
Class: |
A61M 1/3686 20140204;
B01J 20/28035 20130101; B01D 69/141 20130101; B01J 20/28033
20130101; B01J 20/28004 20130101; B01J 20/28026 20130101 |
Class at
Publication: |
210/483 ;
210/488 |
International
Class: |
B01D 024/00; B01D
067/00 |
Claims
That which is claimed:
1. A flexible composite membrane comprising a selected quantity of
a polymeric material and a selected quantity of a particulate
material, said membrane comprising: a polymeric matrix wherein said
particulate is substantially immobilized within said polymeric
matrix; and a selectively permeable skin on the outer surface of
said membrane.
2. The membrane of claim 1 wherein said polymeric material is
selected from the group consisting of polyurethane,
polyvinylidenefluoride, cellulose acetate, polyvinyl chloride and
ethylene vinyl alcohol copolymer.
3. The membrane of claim 1 wherein said polymeric material is
naturally hydrophobic.
4. The membrane of claim 1 wherein more of said particulate
material is disposed within the interior of said membrane than
within said skin.
5. The membrane of claim 1 comprising between about 5% and 30% of
said polymeric material.
6. The membrane of claim 1 comprising about 70% by weight of said
particulate material.
7. The membrane of claim 1 further comprising a support within said
membrane.
8. The membrane of claim 7 wherein said support comprises a
polyester mesh material.
9. The membrane of claim 1 comprising a non-fiberized polymeric
material.
10. The membrane of claim 7 wherein the thickness of said membrane
is between about 100 and 1500 .mu.m.
11. The membrane of claim 7 wherein the thickness of said membrane
is between about 400-1000 .mu.m.
12. A method for making a flexible membrane having a polymeric
matrix and a particulate material immobilized within said matrix,
said method comprising: providing a support having a first
substantially flat surface and a second substantially flat surface;
combining at least a polymeric material and a selected quantity of
particulate material to form a blend; applying a substantially
uniform thickness of said blend to each of said surfaces.
13. The method of claim 12 wherein said polymer solution comprises
a polymer selected from the group consisting of polyurethene,
polyvinylidenefluoride, cellulose acetate and polyvinyl
chloride.
14. The method of claim 12 wherein said polymer is hydrophobic.
15. The method of claim 12 comprising selectively distributing said
particulate material within said membrane.
16. The method of claim 12 wherein said membrane comprises between
5% and 30% of said polymer and 70-95% of particulate.
17. The method of claim 12 wherein said membrane comprises at least
50% by weight of said particulate material.
18. The method of claim 12 comprising dissolving said polymer in an
organic solvent to provide said polymer solution prior to combining
said polymer solution with said particulate material.
19. The method of claim 12 further comprising contacting said
support with a liquid that is a non-solvent for said polymeric
material by immersing said support in a bath of said liquid for a
selected period of time after said applying step.
20. The method of claim 12 wherein said blend is applied to a
continuously moving sheet of said support.
21. The method of claim 19 wherein said support is alternately
immersed in and removed from said water bath.
22. The method of claim 21 further comprising drying said
membrane.
23. The method of claim 22 comprising drying said membrane for at
least 10 minutes at 50.degree. C.
24. The method of claim 12, 14 or 23 further comprising treating
said membrane with a wetting agent or hydrophilizing coating
agent.
25. The method of claim 24 wherein said agent comprises between
0.20% and 1% polyvinyl alcohol.
26. The method of claim 24 wherein said agent comprises
glycerol.
27. The method of claim 24 wherein said agent comprises sodium
chloride.
28. The method of claim 24 further comprising drying said membrane
after said treating.
29. The method of claim 27 wherein said agent comprises 0.9% sodium
chloride.
30. The method of claim 12 further comprising introducing said
support and said blend into a housing wherein said blend is applied
to the surfaces of said support.
31. The method of claim 12 further comprising contouring said
membrane into a pleated sheet.
32. The method of claim 12 further comprising contouring said
membrane into a rippled sheet.
33. The method of claim 30 comprising substantially excluding
particles of said particulate material having a diameter greater
than about 20 .mu.M.
34. The method of claim 12 comprising continuously introducing said
support and said blend into a housing; applying a selected
thickness of said blend to opposite surfaces of said support;
advancing said support with said blend applied thereon into at
least one treatment bath at a rate of approximately 1 ft/min.;
drying said support with said blend applied thereon; and contouring
said dried support with said blend applied thereon into a rippled
sheet.
35. The method of claim 12 wherein said polymeric material
comprises either a) at least two polymers or b) at least two
copolymers or c) at least a polymer and copolymer.
36. The method of claim 22 further comprising cutting said membrane
to a desired size and sealing at least one edge of said
membrane.
37. A flexible composite membrane comprising a selected quantity of
a polymeric material and a selected quantity of fine particles,
said membrane comprising a polymeric matrix wherein said particles
are substantially immobilized within said polymeric matrix, and
wherein the majority of said particles have a diameter less than
about 20.mu..
38. A flexible composite, contoured membrane comprising a selected
quantity of a non-fiberized polymeric material and a selected
quantity of a particulate material, said membrane comprising a
polymeric matrix wherein said particulate is substantially
immobilized within said polymeric matrix.
39. A flexible composite membrane comprising a selected quantity of
a polymeric material and a selected quantity of a particulate
material, said membrane comprising a polymeric matrix wherein said
particulate material is substantially immobilized within said
polymeric matrix, and wherein said membrane has a thickness of at
least about 400 .mu.m.
Description
[0001] The present invention relates to composite membranes and to
methods for making composite membranes. More particularly, the
present invention relates to a novel composite membrane that
includes a particulate material immobilized within a polymeric
matrix and to a method for making such a membrane. The methods and
apparatus employing such a membrane are particularly useful for
removing organic compounds that have been added to a biological
fluid, such as blood, as part of a pathogen inactivation
treatment.
BACKGROUND OF THE INVENTION
[0002] Human blood includes both cellular and non-cellular
components. The cellular components in blood include red blood
cells (RBC), white blood cells (WBC), and platelets. Plasma is a
non-cellular component of blood and is the liquid medium in which
the cellular components are suspended. Plasma also includes various
other components such as proteins, compounds that assist in blood
coagulation (coagulation factors), electrolytes and
metabolites.
[0003] During or after collection, human whole blood is commonly
separated into its various components (RBC, WBC, platelets,
plasma). Typically, the separated components may be stored for some
period of time, and transfused to a patient in need of a particular
blood component. For example, collected plasma may be transfused to
a patient to provide plasma proteins and coagulation factors, or to
replace lost blood volume. Platelets may be administered to cancer
patients whose ability to produce platelets has been destroyed by
chemotherapy and/or radiation treatment. RBCs may be administered
to patients who have experienced rapid blood loss, or to improve
the oxygen carrying capability of blood in patients suffering from
anemia and the like.
[0004] It is now well known that viruses such as hepatitis B,
hepatitis C, human immunodeficiency virus (HIV), cytomegalovirus
and T-cell lymphotrophic virus (HTLV) may be resident within human
blood and within the blood components. Certain bacteria such as
Yersinia enterocolitica may also reside within human blood. The
presence of virus and/or bacteria, (collectively referred to herein
as "pathogens") in the blood stream poses the risk of infection and
disease not only to the host, but also to a healthcare provider
handling the blood, and/or if the collected blood or blood
component is to be transfused, to the recipient of such blood or
blood components. Accordingly, the medical community has attempted
to reduce the risk of transfusing blood that contains such
pathogens by developing methods and apparatus to remove or
inactivate pathogens found in the blood component. As used herein,
"pathogen inactivation" (and forms thereof) means, generally,
rendering a pathogen harmless to a living being. Pathogen
inactivation includes killing, destroying, or eradicating a
pathogen (either viral or bacterial), or either directly or
indirectly inhibiting the ability of the pathogen to replicate.
"Pathogen inactivating compounds" refers to compounds used in
pathogen inactivation, including the decomposition products of such
compounds.
[0005] One early attempt of removing virus from blood involved the
filtration of blood and blood components to remove intracellular
viruses entrained, for example, in white blood cells, Rawal et al.,
"Reduction of Human Immunodeficiency Virus-Infected Cells From
Donor Blood by Leukocyte Filtration," Transfusion, pages 460-462
(1989).
[0006] Other prior methods for inactivating viruses and, in
particular, extracellular viruses in blood, include steam
sterilization of blood plasma and use of "detergents" to cleanse
the blood or the blood component of the pathogens.
[0007] Pathogen inactivation has also been proposed by treating
blood or blood components with a photochemical agent and light,
referred to as "photoactivation". When activated by light of an
appropriate wavelength, the photochemical agent either kills the
virus directly or indirectly inhibits the ability of the virus to
replicate and, thus, in either case "inactivates" the virus.
Several known photochemical agents have been used or disclosed for
use in inactivating viruses in blood, including psoralens, as
described in U.S. Pat. No. 5,459,030; pthalocyanines, as described,
for example in Rywkin, S. et al. Photochem. Photobiol. 60:165-170
(1994); and phenothiazine dyes, including without limitation,
toluidine blue O, szure A, azure B, azure C, thionine, methylene
blue and dimethylmethylene blue. For example, U.S. Pat. No.
5,527,704, incorporated by reference herein, discloses methods and
apparatus for inactivating viruses in biological fluid in which a
biological fluid (e.g., plasma) is combined with methylene blue and
subjected, for a period of time, to light of a suitable intensity
and wavelength for activating the methylene blue.
[0008] Other methods for treating biological fluid such as blood or
blood components which do not involve photoactivation are also
known. For example, International Publication No. W098/070674
describes mustards linked to aziridines. U.S. Pat. Nos. 5,691,132
and 5,559,250 (which are incorporated by reference herein) describe
methods for treating a biological fluid that includes RBCs by
contacting the RBCs with a compound having a nucleic acid binding
ligand and a mustard group. It is believed that such compounds
react with nucleic acids of the pathogen (both viral and bacterial)
to form covalent complexes that inhibit replication of the
pathogen. Examples of acridine compounds include, but are not
limited to, compounds such as N1, N1-bis (2-chlorethyl)
-N4-(6-chloro-2-methoxy-9-acridinyl) -1,4 pentanediamine.
[0009] It may also be desirable to include certain other organic
compounds in the above described treatment system to enhance the
effectivity of the pathogen inactivating compound by reducing or
"quenching" potential side reactions of the pathogen inactivating
compound. For example, inclusion of certain naturally occurring
tripeptides such as, but not limited to reduced L-glutathione
quenches potential side reactions and allows for maximum pathogen
inactivation by the pathogen inactivating compound. Other examples
of quenchers useful in pathogen inactivation processes may include
sulfydryls such as mercaptoethanol, as described in Rywkin, S. et
al. Transfusion 35:414-20 (1995), cystein, quercitin, as described
in Ben-Hur et al, Photochem. Photobiol 57:984-8 (1993) and rutin,
as described in Margolis-Nunno, Transfusion 35:852-862 (1995).
[0010] As many of the pathogen inactivation methods known to date
involve addition of either (1) compounds not normally present in
blood (e.g., photochemical dyes, nucleic acid binding agents with
mustard groups) or (2) concentrations of compounds (e.g.,
L-glutathione) in excess of typical concentrations found in human
blood, it is desirable to remove substantially as much of the added
compounds as possible from the treated biological fluid, prior to
transfusion to a patient or other recipient.
[0011] For example, methods and devices for separating photoactive
agents used in pathogen inactivation are described in U.S. Pat. No.
5,660,731. In that patent, photochemical agents such as methylene
blue are separated from blood by contacting the photochemical agent
with a porous medium that includes, for example, activated carbon
fibers. The porous medium may be in the form of a web, sheet,
cylinder or included in a filter with an inlet and outlet through
which the biological fluid passes and, thus, contacts the porous
medium.
[0012] A similar approach is described in U.S. Pat. No. 5,639,376
which discloses a filter for removing leukocytes and a viral
inactivating agent such as methylene blue, its metabolites and
photodecomposition products, from plasma or other blood fractions.
As in U.S. Pat. No. 5,660,731, removal of the antiviral agent is
achieved by contacting the blood with a filter adapted for
removing, for example, both leukocytes and the antiviral agents.
The filter includes activated carbon as a sorbent for methylene
blue.
[0013] U.S. Pat. No. 4,728,432 more generally describes methods and
devices for removing poisonous substances contained in blood by
means of sorption. The sorbents described in that patent include,
for example, activated carbon fixed to a support member. The
activated carbon is combined with a polymer.
[0014] Other examples of methods and devices for removing organic
compounds from a biological fluid are described in U.S. patent
application Ser. No. 09/003,113, entitled "Methods and Devices for
the Reduction of Small Organic Compounds from Blood Products" which
is incorporated by reference herein. That application describes
using sorbent particles such as activated carbon beads applied to a
support for removal of, for example, acridine, acridine
derivatives, methylene blue or thiols in a blood product. The
activated carbon beads may be contained within a pouch or overwrap,
or captured within a fiberized matrix, or captured within a
fiberized matrix and contained within a pouch or overwrap.
SUMMARY OF INVENTION
[0015] The present invention is directed to a flexible composite
membrane that includes a selected quantity of a polymeric compound
and a selected quantity of a particulate material. The membrane
includes a polymeric matrix with the particulate material
substantially immobilized within the polymeric matrix. In
accordance with one aspect of the present invention, the composite
membrane includes a selectively permeable skin on the outer surface
of the membrane.
[0016] In accordance with another aspect of the present invention,
the flexible composite membrane includes a selected quantity of
fine particles immobilized within the polymeric matrix where the
majority of the particles have a diameter of less than about 20
.mu.m. In accordance with another aspect of the present invention,
the flexible composite membrane is contoured and includes a
selected quantity of a non-fiberized polymeric material and a
selected quantity of particulate material. The membrane includes a
polymeric matrix and the particulate is substantially immobilized
within the polymeric matrix.
[0017] In accordance with still another aspect of the present
invention, the membrane includes a selected quantity of a polymeric
material and a selected quantity of a particulate material. The
membrane includes a polymeric matrix with the particulate material
substantially immobilized within the polymeric matrix. The membrane
has a thickness of at least about 400 .mu.m.
[0018] The present invention is also directed to a method for
making a flexible, composite membrane having a polymeric matrix and
a particulate material immobilized by the polymeric matrix. The
method may include, for example, providing a support having a first
substantially flat surface and a second substantially flat surface.
The method includes combining a polymer solution and a selected
quantity of a particulate material to form a blend. A uniform
thickness of the blend is applied to the surfaces of the support.
In accordance with another aspect of the present invention, the
membrane is treated with a wetting agent.
DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view of a container that includes a
membrane embodying the present invention;
[0020] FIG. 2 is a perspective view of a container including an
alternative embodiment of a membrane embodying the present
invention;
[0021] FIG. 3 is an enlarged, partial, side, cross-sectional view
of a membrane (with a support) made in accordance with the present
invention taken along 3-3 of FIG. 1;
[0022] FIG. 4 is an enlarged, partial, side, cross-sectional view
of a membrane (without a support) made in accordance with the
present invention;
[0023] FIG. 5 is a side cross-sectional view of the container and
membrane of FIG. 1 taken along 5-5;
[0024] FIG. 6 is a side cross-sectional view of the container and
membrane of FIG. 2 taken along 6-6;
[0025] FIG. 7 is a side cross-sectional view of an alternative
embodiment of the container and a membrane embodying the present
invention;
[0026] FIG. 7A is a side cross-sectional view of an alternative
embodiment of the container and membrane embodying the present
invention;
[0027] FIG. 8 is a diagram of the apparatus and method used for
making membranes in accordance with the present invention;
[0028] FIG. 9 is an enlarged perspective view of one stage of the
apparatus and method shown in FIG. 8, in which a polymer
solution/particulate blend is applied to a support;
[0029] FIG. 10 is an enlarged cross-sectional side view of the
apparatus of FIG. 9 taken along line 10-10 of FIG. 9;
[0030] FIG. 11 is a perspective view of an apparatus useful in the
method of making membranes of the present invention;
[0031] FIG. 12 is a cross-sectional side view of the apparatus of
FIG. 11 taken along 12-12;
[0032] FIG. 13 is a side view of another embodiment of a membrane
made in accordance with the present invention;
[0033] FIG. 14 is a photograph of a cross-sectional view of an
actual membrane (magnified approximately 100.times.) embodying the
present invention, using a scanning electron microscope;
[0034] FIG. 15 is a photograph of a cross-sectional view of an
actual membrane (magnified approximately 3300.times.) embodying the
present invention, using a scanning electron microscope;
[0035] FIG. 16 is a photograph of a cross-sectional view of an
actual membrane (magnified approximately 1500.times.) embodying the
present invention, taken near the support, using a scanning
electron microscope;
[0036] FIG. 17 is a photograph of a cross-sectional view of an
actual membrane (magnified approximately 1600.times.) embodying the
present invention, taken near the outer surface of the membrane,
using a scanning electron microscope;
[0037] FIG. 18 is a photograph of the surface of an actual membrane
(magnified approximately 270.times.) embodying the present
invention, using a scanning electron microscope;
[0038] FIG. 19 is a photograph of the surface of an actual membrane
(magnified approximately 5500.times.) embodying the present
invention , using a scanning electron microscope;
[0039] FIG. 20 is a photograph of the surface of an actual membrane
(magnified approximately 37,000.times.) embodying the present
invention, using a scanning electron microscope
[0040] FIG. 21 is a photograph of activated charcoal powder
particles (magnified approximately 400.times.), using a scanning
electron microscope;
[0041] FIG. 22 is a photograph of activated charcoal powder
particles (magnified approximately 3300.times.) using a scanning
electron microscope;
[0042] FIG. 23 is a photograph of activated charcoal powder
particles (magnified approximately 37,000.times.) using a scanning
electron microscope;
[0043] FIG. 24 is a graph showing the rate of sorption of methylene
blue by a membrane made in accordance with the present
invention;
[0044] FIG. 25 is a graph showing the rate of sorption of
L-glutathione by a membrane made in accordance with the present
invention;
[0045] FIG. 26 is a graph showing the sorption of an acridine
derivative in packed RBC by a membrane made in accordance with the
present invention;
[0046] FIG. 27 is a graph showing the sorption of L-glutathione in
packed RBC by a membrane made in accordance with the present
invention; and
[0047] FIG. 28 is a graph showing the percent hemolysis in packed
RBC treated with an acridine compound and L-glutathione and
contacted with a membrane made in accordance with the present
invention.
DETAILED DESCRIPTION OF DRAWINGS
[0048] Turning now to the drawings, the present invention is shown,
for purposes of illustration only, in connection with removal of
pathogen inactivating compounds, including pathogen inactivating
agents, their by-products and/or other added organic compounds
employed in a pathogen inactivation process. As described more
fully below, certain aspects of the present invention, such as the
membrane and the method for making the membrane, have application
beyond the field of pathogen inactivation of biological products.
For example, the membrane and method for making it may have
application in any other field or industry where it is desired to
have an apparatus (such as membrane, tube, rod etc.) in which a
particulate material is immobilized by or within a polymeric
matrix. Accordingly, while the detailed written description of this
invention is generally in the context of pathogen inactivation of
biological fluids, such as blood components, the scope of the
present invention is set forth in the appended claims.
[0049] FIG. 1 shows a membrane 10 made in accordance with the
present invention inside a plastic container 12 suitable for
holding a biological fluid, such as, but not limited to, blood and
blood components. As shown in FIG. 1, membrane 10 may be in the
shape of a flat sheet or, alternatively, pleated as shown in FIGS.
2 and 6 or rippled, as shown in FIG. 13. A pleated or rippled sheet
enhances contact of the membrane surface with the compounds to be
removed. Although the membranes 10 specifically shown in FIGS. 1
and 2, occupy much of the cross-sectional area of the container
interior, it should be understood that the size and dimensions of
the membrane sheet may be varied without departing from the present
invention. Also, it will be understood that the present invention
is not limited to sheet membranes (flat, pleated or rippled), but
may also be embodied in other configurations such as fibers, rods,
tubes and the like. Also, membranes made in accordance with the
present invention may be housed in a device having a flow inlet and
flow outlet. The device may include a substantially flat membrane
where the flow of fluid is transverse to the membrane surface, or
may include a rippled or pleated membrane whereby the areas between
the ripples or pleats provide flow channels for axial flow of the
fluid.
[0050] Turning briefly to a discussion of the container, container
12 may be made of any polymeric material that is typically used for
making biomedical containers. For example, the container may be
made of a polyvinyl chloride (PVC) that has been plasticized with a
plasticizer such as DEHP, TEHTM, citrate ester or other known,
biocompatible plasticizers. Alternatively, the container may be
made of a non-PVC plastic, such polyolefin with or without a
plasticizer. Examples of suitable biocompatible containers for
storing biological fluid include the containers described in U.S.
Pat. Nos. 5,167,657, 5,100,401 and 5,026,347.
[0051] Returning now to a description of the membrane 10, as
generally shown in FIGS. 3 and 4, membrane 10 is a composite of a
polymeric material and a particulate material (shown as specs)
within the polymeric matrix 16 of the membrane. Membrane 10 may
optionally, include a support 18 (FIG. 3) or be made without a
support (FIG. 4). As shown in FIG. 3, for example, support 18 forms
the core of the membrane 10 and provides a substantially open
structure within the continuous matrix 16 of the membrane. The
outer surface of membrane 10 may further include a "skin" 19
(described in more detail below). As shown in FIG. 3 and in FIG.
18, the skin 19 may include randomly spaced surface pores 21.
[0052] In another alternative, shown for example in FIG. 7, the
membrane 10 may be supported directly by the interior of the
container wall 12 (i.e., the container wall acting as a support).
In still another alternative, the edges of membrane 10 may be held
by the sealed walls 13 of container 12 as shown in FIG. 7A.
[0053] Support 18 may be made of any material to which the
polymeric material will adhere including, for example, polymers,
glass, cloth or other fibrous material, (as shown, for example, in
FIG. 3 wherein the fibers 18a may be seen). In one embodiment, the
support may be a polyester mesh material. Such a material is
available as Hollytex 3257 from Ahlstrom Corp. of Mount Holly
Springs, Pa.
[0054] As described above, membrane 10 may be made of a polymeric
material (such as a polymer or copolymer) and a selected amount of
a particulate material immobilized within the polymeric material.
The polymeric material may be a polymer (including elastomers), a
copolymer, mixtures of polymers, mixtures of copolymers or mixtures
of polymers and copolymers. If membrane 10 is to be used in
conjunction with a biological fluid, the polymeric material should
not deleteriously affect the biological fluid which it contacts.
The polymeric material should also be substantially miscible With
the particulate material. Typically, the polymeric material may be
hydrophilic, but may also be a hydrophobic polymeric material that
is capable of being hydrophilized. Examples of polymeric materials
suitable for use in the membrane of the present invention include,
but are not limited to, polyurethane, cellulose acetate,
polyvinylidene fluoride (PVDF) polyvinyl chloride (PVC),
thermoplastic elastomers (such as those sold under the name Hytrel)
and ethylene vinyl alcohol copolymer. Particularly useful in the
present application are the polyurethanes. Polyurethanes are
available from a variety of suppliers, such as Morton International
Inc. The polyurethanes Morthane PNO3 and Morthane PB355, are
presently preferred.
[0055] The particulate material should likewise be capable of being
combined with the selected polymer. Where the membrane 10 is used
to absorb selected organic compounds from a biological fluid, the
particulate material may be a sorbent. Sorbents in powdered form
may be preferred (over, for example, beads or other larger
particles) so that the membrane will have a smoother surface and,
thus, be less abrasive to the fluid which it contacts and the
components therein. In addition, a powdered sorbent may be more
effectively immobilized by the polymer. of course, selection of the
sorbent may also depend, in part, on the affinity of the compound
to be removed for the particular sorbent.
[0056] Activated charcoal is a known sorbent and is the preferred
sorbent for the present invention. Activated charcoal is available
in bead form, however, for reasons set forth above, activated
charcoal in a powdered form may be preferred. Activated charcoal is
also available from a variety of sources. Examples of activated
charcoal include activated charcoal powders available from
Norit.RTM. Americas Inc. of Marshall, Tex. such as Norit Pac 200,
Darco S51FF, Darco KB-B, Norit SX Ultra, G-60 Norit.RTM. A Supra,
Norit.RTM. B Supra and Norit E.RTM. Supra. Typically, the particles
of activated charcoal are porous and have a diameter of less than
about 20.mu. or even less than 10.mu. and have a total surface area
of greater than about 1000 m.sup.2/g. Particularly useful in making
the membranes of the present application is Norit A Supra activated
charcoal powder. For example, in Norit.RTM. A Supra, most of the
particles have a diameter of less than about 20 .mu. and a
substantial number have a diameter of less than about 10.mu..
Norit.RTM. A Supra has typical total surface are of about 2000
m.sup.2/g. Of course, other activated charcoals may also be used.
Other examples of particulate materials suitable for use in the
present invention include microporous polystyrene sorbent beads
which, preferably, may be ground to provide smaller particles
having a diameter of about 20 .mu.m or less.
[0057] As discussed in more detail below, the above-described
polymeric materials and particulate materials are combined to form
a slurry-like blend used to make membrane 10. The blend includes
(1) a polymer solution derived from a polymeric material dissolved
in a solvent and (2) the particulate. Alternatively, the blend may
include a molten polymer (i.e., no solvent) and particulate. As
used herein, "blend" refers to the polymeric material (either as a
polymer solution or molten polymer) and the particulate material.
In accordance with the present invention, it is desirable that the
amount of solids in the blend (i.e., excluding the solvent) include
anywhere between about 40%-90%, by weight, of the particulate
material and between about 10%-60%, by weight, of the polymeric
material. In one embodiment, the amount of particulate (by weight)
in the blend should be greater than 50% (of the solids).
Preferably, the solids in the blend may include approximately 70%
of the particulate material and approximately 30% of the polymeric
material.
[0058] Membranes of the type described above (and, in particular,
those derived from a blend of a polymer solution and particulate)
may be made, for example, by flow casting or extruding the blend
onto a support 18 using the apparatus 20 generally depicted in FIG.
8. As shown in FIG. 8, apparatus 20 may include a rolled sheet of
support 18. Support is dispensed (from dispenser 22) into a
v-shaped chamber 24 that receives the sheet of support and the
blend. The blend is applied to the outer surfaces of the support 18
(as shown in FIG. 9) within the chamber. The support with blend
applied thereon exits the chamber through an opening at the bottom
of the chamber 24. Of course, the membrane of the present invention
may also be made without an integral support by, for example,
applying the blend to a drum and, thereafter, peeling the membrane
off the surface of the drum (and further processing the membrane as
described below). In any event, whether the membrane 10 is made
with or without a support, apparatus 20 may include one or more
baths 26 and 28 containing solutions used in the process of making
the membrane. Apparatus 20 also may include drying oven 30.
Optionally, apparatus 20 may include additional bath 32 and oven 34
for further post-drying treatment of membrane 10. Typically,
apparatus 20 includes a series of rollers 36 over which the
membrane is threaded as generally shown in FIG. 8. Rotation of the
rollers 36 effects movement of the membrane from dispenser 22,
through the series of baths 26, 28, 32 and ovens 30 and 34.
Finally, if desired, equipment for winding 38 and slitting the
membrane 10 to its desired width may also be included.
[0059] In accordance with one method of making the membrane of the
present invention, the polymeric material and the particulate
material are combined in the proportions generally described above.
Specifically, the polymeric material may first be dissolved in a
suitable solvent. A variety of solvents may be used for different
polymeric materials. For exemplary purposes only, where the polymer
is a polyurethane or cellulose acetate, a suitable solvent may be
N-methylpyrrolidone (NMP). A suitable solvent for PVC may be
tetrahydrofuran, while a suitable solvent for PVDF may be
dimethylacetamide (DMAC). of course, it will be appreciated by
those of skill in the art that other solvents may also be used.
[0060] A selected amount of the particulate material may then be
added to the dissolved polymeric material (polymer solution) to
provide the slurry-like blend. The blend is then introduced into
chamber 24 through which support 18 has been threaded. As shown in
more detail in FIGS. 9 and 10, chamber 24 is generally v-shaped and
includes gap 40 at the bottom through which the support 18 exits.
The width of gap 40 may be adjusted to accommodate different
thicknesses of support 18 and also to control, in part, the
thickness of the blend coated on support 18.
[0061] As shown in FIG. 10, the lower portion of chamber 24
includes a narrow passageway 41 defined by downwardly extending
walls (or land) 43. As the blend flows into the passageway 41,
shear forces generated between the walls 43 and support 18 may urge
the particles within the blend away from the walls 43 and toward
the center of the membrane. Thus, it is presently believed that
more of the particles may be distributed within the inner portions
of the membrane than at or near the outer surfaces, (as generally
shown, for example, in FIGS. 3 and 4) thus effectively providing
the membrane with a "skin" portion over the interior of the
membrane and, more specifically, the polymeric matrix. As more of
the particles are disposed within the interior of the membrane than
in or near the skin, it is less likely that particles will become
dislodged from the membrane and enter the fluid with which membrane
10 is in contact during use. It is also believed that larger
particles having, for example, a diameter greater than about 20
.mu.m are excluded from entering passageway 41 and, therefore, are
not included in the membrane. This may be desirable from the
standpoint that larger particles may not be as effectively
immobilized by or within the polymeric matrix. Thus, excluding
larger particles decreases the possibility that particulate will
become dislodged from the polymer and enter the fluid with which
membrane 10 is in contact with during use.
[0062] In addition, walls 43 may also assist in providing that the
thickness of the blend on either side of the support 18 is
symmetric and uniform by ensuring that support 18 is properly
centered within gap 40. It is believed that if support 18 is not
properly centered within gap 40, the shear forces on either side of
the support within passageway 41 will not be equal. The greater
pressure on one side of the support 18 may shift the support back
to the center of the gap 40. Thus, the apparatus of the present
invention provides for a "self-centering" membrane that will
receive a uniform coating of the blend. In one embodiment, the
length of passageway, as defined by walls 43, may be between 0.5-3
cm in length.
[0063] In an alternative embodiment of the present invention, a
second v-shaped chamber (shown in broken lines as chamber 25 in
FIG. 8) may be used to apply an additional polymeric material to
the membrane (to, for example, provide a protective coating and
further prevent the particulate material near the surface of the
membrane from becoming dislodged.) The second chamber may be placed
in series with and below chamber 24, such that upon exiting chamber
24, support with the blend applied thereon enters the second
chamber 25. The second chamber may, for example, include a
different polymeric material or a more dilute concentration of the
polymeric material used to make the blend, which may include a
lower concentration of particulate material or no particulate
material at all.
[0064] As shown in FIGS. 9 and 10, the blend may be applied to both
sides of support 18. However, it will be understood that,
optionally, only one side of the support 18 may be coated with the
blend. In any event, the coated support is introduced into a first
coagulation bath 26. Typically, in the first coagulation bath 26,
the blend is contacted with a liquid or solution which is a
non-solvent for the polymer portion of the polymeric solution, but
is freely miscible with the solvent portion of the polymer
solution. Contact with the liquid or solution coagulates the solids
(polymer and particulate) and exchanges the liquid portion so that
on exiting bath 26, the polymeric material/particulate blend
includes two continuous but separated phases. One phase includes
the polymeric material with embedded particulate and the other
phase includes the non-solvent liquid.
[0065] Rotation of the rollers 36 advances the membrane 10 from
coagulation bath 26 to one or more extraction baths 28. Typically,
extraction baths 28 contain a solution that will extract from the
membrane any residual solvent used to dissolve the polymer.
Depending on the type and strength of solvent, the membrane may
undergo a series of wash steps, each bath further washing and
removing solvent from the membrane. For purposes of example only,
three (3) extraction baths 28 are shown in FIG. 8.
[0066] Once the solvent has been substantially extracted from the
membrane, the membrane may be dried. As shown in FIG. 8, after the
final extraction bath, the membrane may be introduced into an oven
30 such as an air circulating oven. Of course, other forms of
drying may also be used including air drying or contacting the
membrane with a heated surface.
[0067] Prior to or after drying, the membrane 10 may be further
treated with a surfactant or other agent to, for example, make the
membrane 10 hydrophilic, prevent the loss of wettability (as a
result of drying) or restore the wettability of the membrane which
may have been lost or diminished as a result of drying. Thus, as
shown in FIG. 8, the membrane may be introduced into another bath
32 containing the wetting agent or hydrophilizing coating agent.
The method of applying the surfactant is not limited to immersing
it in bath 32, but may also include spraying or other forms of
applying the surfactant to the membrane. If treated with a treating
agent, further drying in oven 34 may be desired. The membrane may
then be cut (to its desired width) and wound up on apparatus 38.
Membrane 10 may further be cut into smaller lengths for inclusion
in a container 12. The edges of the cut membrane 10 may be enclosed
or treated with an epoxy or other sealant.
[0068] As set forth above, the membrane may be further contoured
into a pleated or rippled sheet. An apparatus 44 for forming a
rippled membrane is shown in FIGS. 11-12 and the resultant membrane
10, is shown in FIG. 13. As shown in FIGS. 11-12, apparatus 44 may
include a series of stacked rods 46, the ends of which are retained
within slots 48 of support member 50. Membrane 10 is woven between
rods 44 as substantially shown in FIG. 12. Apparatus 44 with woven
membrane 10 is heat set for approximately 10-30 minutes at a
temperature suitable for the polymer. For example, where the
polymer is polyurethane, a typical temperature may be approximately
100.degree. C. and a typical heating time may be approximately 15
minutes. After heating, the membrane retains a rippled shape as
shown in FIG. 13. Of course, it will be appreciated that other ways
of contouring (i.e., rippling, pleating) the membrane are also
possible without departing from the present invention. The finished
membrane 10 may then be sterilized by, for example, gamma
radiation.
[0069] In a specific embodiment, membrane 10 is made of a
polyurethane and activated charcoal powder. For example,
polyurethane is dissolved in a solvent such as N-methylpyrrolidone
(NMP). Between approximately 5%-20% by weight of polymer may be
combined with approximately 80%-95% by weight of solvent to
dissolve the polymer. Preferably, where the polymer is polyurethane
the amount of polymer is between about 6%-15% of the total
polymer/solvent weight. As used herein, the polymer solution is
expressed as the percentage (in weight percent) of the polymer in
the solvent. Thus, for example, 10 grams of polyurethane may be
combined with 90 grams of NMP to provide a 10% polymer solution.
The resulting polymer solution is then combined with the
particulate material to form the blend.
[0070] As used herein, the composition of the blend is expressed as
the weight percentage of a particulate material (such as activated
charcoal) in the combined amount of particulate and polymer (the
solids). Thus, for example, 10 grams of activated charcoal (or
other particulate) added to the polymer solution that includes 10
grams of polymer and 90 grams of solvent, would provide a membrane
having 50% charcoal and 50% polymer. Similarly, 30 grams of
activated charcoal (particulate) added to a polymer solution having
10 grams of polymer (polyurethane) would result in a membrane
having a 75% "loading" of activated charcoal (or other particulate)
and 25% polyurethane (i.e., 30 grams of particulate in 40 (10+30)
grams of polymer and particulate is a 75% loading of particulate).
In any event, the amount of activated charcoal should be at least
10% by weight and preferably 70% by weight.
[0071] After blending the activated charcoal with the polymer
solution, the blend is then introduced into the chamber 24 as
described above and may be applied to a polyester mesh material
supplied from dispensing roll 22. In a preferred embodiment, the
blend is applied to both sides of the polyester support, as shown
in FIGS. 9 and 10, to achieve a total membrane thickness (film and
support) 44 of approximately between 250 and 1000 micrometers and,
preferably, 400-1000 micrometers. It has been observed that to
achieve a membrane thickness of approximately 400-1000 micrometers,
gap 40 in chamber 24 should be slightly wider than the desired
thickness of the membrane and may measure, for example, between
about 600-1200 micrometers. More specifically, it has been observed
that to provide a polyurethane membrane with 70% activated charcoal
powder having a thickness of about 500 .mu.m, gap 40 should be
approximately 705 .mu.m, and to provide a polyurethane membrane
with 70% activated charcoal powder having a thickness of 1000
.mu.m, gap 40 should be approximately 1105 .mu.m. The membrane 10
is then introduced into coagulation bath 26 which, in the case of
the polyurethane/activated charcoal blend described above, may
include only water. As presently understood, exposure of the blend
to water causes the polymeric blend to coagulate (because
polyurethane is not miscible with water). As coagulation of the
polymer proceeds, solvent NMP leaves the polymer in exchange for
water. Further removal of solvent from the membrane occurs as the
membrane is successively introduced to and removed from a series of
extraction baths 28.
[0072] The rate of movement of the membrane 10 through the
coagulation 26 bath, extraction baths 28 and ovens 30 and 34 may be
controlled (by, for example, a human operator) by adjusting the
rate of rotation of the rollers 30. For example, in one embodiment
where the membrane includes 70% activated charcoal in a 10%
polyurethane solution, the membrane advances through the
coagulation, extraction baths and drying ovens at approximately
between 1-4 ft/min and, typically 1 ft/min. This ensures, for
example, that the solvent (NMP) is substantially extracted from the
membrane, results in a thickness of the membrane that is within the
preferred range, provides for sufficient drying and ensures that
membrane is sufficiently treated with surfactant, if such treatment
is desired. Of course, for polymers other than polyurethane,
different solutions for coagulation/extraction, different line
speeds to either shorten or lengthen the residence time of the
membrane in the coagulation and extraction baths may be desirable
or even required. For example, if the polymer is PVDF, the
coagulation bath may include methanol.
[0073] After extraction of the NMP solvent, membrane 10 may be
dried in oven 30 for anywhere between 10 and 30 minutes at a
temperature of at least 40.degree. C. and typically 50.degree.
C.
[0074] Membrane 10 may be treated with a wetting agent or
hydrophilizing coating agent (hereinafter "treating agent") in bath
32 to enhance the sorption characteristics of membrane 10, prevent
the loss of wettability after drying or restore lost or diminished
wettability of the membrane caused by drying. The treating agent
may be a compound (dissolved in an appropriate solvent) that is
capable of hydrophilizing the membrane 10. For example, the
treating agent may be polyvinyl alcohol (PVOH) dissolved in an
isopropyl alcohol/water solution. Specifically, where the polymer
is made of polyurethane with activated charcoal, the hydrophilizing
bath may include between approximately 0.20%-1.5% PVOH in an
approximately 50/50 water/isopropyl alcohol solution. For membranes
made of polyurethane and activated charcoal, 0.25% up to about 1%
PVOH solutions may be preferred.
[0075] Other solutions may also be used to treat the membrane 10
and make it more hydrophilic. Specifically, solutions including
sodium chloride are suitable, including solutions that include
0.45% NaCl or 0.9% NaCl. This may include, for example, solutions
commonly used in the storage of red blood cells, such as Adsol.RTM.
(described in U.S. Pat. No. 4,267,269 incorporated by reference
herein). Still other solutions that may be used to treat the
membrane include 1-10% glycerol in isopropyl alcohol, polyethylene
oxide (PEO) and/or blends of PEO and polyurethane in 70/30, 50/50,
30/70, isopropyl alcohol/water solutions. Where the membrane is
used with a biological fluid, such as blood, membrane 10 may also
be treated with an agent that further improves the
hemocompatability of the membrane relative to retain compounds or
biological components. One such agent is
polyhydroxyethylmethacrylate or pHEMA. In any event, the membrane
10 may be treated with the above described solutions prior to or
after drying.
[0076] Membranes made in accordance with the present invention
provide a unique and cost effective way of immobilizing fine
particulate powder that is typically difficult to handle and prone
to shedding. This is particularly advantageous in the field of
blood therapy where introducing foreign particles into the blood or
other biological fluid is considered undesirable. The membranes
made in accordance with the present invention are also unique, in
part, because the particulate is substantially captured by the
polymer matrix without compromising the ability of the powder to
act as a sorbent for organic compounds used in pathogen
inactivation treatments. As presently understood, the fine powder
is widely dispersed across the polymeric matrix and, therefore,
provides a multitude of sorption sites for the molecules of the
organic compounds. The broad dispersal of powder may also mean that
molecules of the organic compounds will have to travel shorter
distances before they are captured by the sorbent powder.
[0077] Actual membranes made in accordance with the present
invention are shown in FIGS. 14-20. In particular, FIGS. 14-20 show
a membrane made from a blend derived from a 10% polyurethane
solution (PNO3) to which was added Norit.RTM. A Supra activated
charcoal powder to obtain a charcoal loading of approximately 70%
(i.e., the solids comprise 70% activated charcoal and 30%
polyurethane). The membrane was prepared using the apparatus
generally depicted in FIG. 8 (using a single chamber 24) and
described herein. A polyester mesh was used as a support.
[0078] The resultant membrane includes a polymeric matrix which, in
FIG. 14, appears as an array of sponge-like structures. As further
seen in FIG. 14, the polymeric matrix is substantially continuous
throughout the membrane, even across portions of the polyester mesh
support. The polyester mesh support is seen, in cross section, as
the larger circular or oval structures near the center of the
membrane. The top and bottom surfaces of the polymeric matrix
include a thin "skin" layer. As seen in FIGS. 15-17, it is believed
that the semi-spherical, grain-like bodies may be particles of
activated charcoal immobilized within the polymeric matrix.
[0079] FIG. 18 is a photograph of the surface of the membrane and,
more particularly, the skin. As seen in FIGS. 18 and 19, the skin
is not completely continuous, but includes randomly spaced voids
across the membrane. When magnified, charcoal particles held by the
polymeric material near the surface of the membrane may be seen
(FIGS. 19 and 20). As seen in FIG. 20, the activated charcoal
particle coated with the polymeric material has a textured look,
not seen in the photographs of the activated charcoal particles
alone (FIGS. 23-25). It is believed that the skin layer of the
polymeric matrix assists in preventing the particles from
dislodging. Significantly, while providing this protective
function, the skin layer does not interfere with mass transport and
remains permeable to certain molecules of the organic compounds to
be removed. When used in pathogen inactivation processes, the
membrane skin is permeable to certain pathogen inactivation
compounds but not, for example, to cellular or other components
found in blood.
[0080] To test the effectiveness of the membranes of the present
invention, samples of prepared membranes were contacted with
solutions containing various compounds commonly used in pathogen
inactivation procedures. The test procedures and results are
described below.
[0081] Membranes of polyurethane and activated charcoal were
prepared as substantially described above. The
polyurethane/activated charcoal blend included 10% of the
polyurethane PNO3 combined with 90% NMP solvent. Activated charcoal
was added to obtain an activated charcoal loading of 70%. The blend
was applied to a polyester mesh support as substantially described
above to form a membrane. Two membranes were dried and treated with
either 1) 0.25% PVOH in a 50/50 water/isopropyl alcohol solution or
2) 0.9% NaCl solution. Other membranes served as controls and were
either dried only (and not treated with any solution) or not dried
at all.
EXAMPLE 1
[0082] A solution containing 50 .mu.m methylene blue phosphate
buffered saline was prepared and distributed into test tubes.
Samples of the membranes prepared as described above were placed in
each test tube. The ratio of membrane surface to fluid was
approximately 2.0 cm.sup.2/ml. Samples were then taken from the
test tubes at timed intervals. The degree of sorption of methylene
blue was measured by spectroscopic means (at 630 nm). The results
are shown in FIG. 24.
EXAMPLE 2
[0083] A solution containing 6 mM reduced L-glutathione in
phosphate buffered saline was prepared and distributed into test
tubes. Samples of the membranes prepared as described above were
placed in each test tube. The ratio of membrane surface to fluid
was approximately 2.0 cm.sup.2/ml. Samples were then taken from the
test tubes at timed intervals and the degree of sorption was
determined by high performance liquid chromatography (HPLC). The
results are shown in FIG. 25.
EXAMPLE 3
[0084] A membrane, having a 70% loading of activated charcoal in a
10% polyurethane (PNO3) solution was prepared as substantially
described above. The membrane was cut into two 22.7.times.10.7
cm.sup.2 sheets and placed inside of two separate 1 liter blood
bags. Two units (approximately 300 ml each) of packed RBC were
prepared by standard blood banking procedures and the acridine
derivative (5-[.beta.-carboxyethyl) amino} acridine (abbreviated as
AD) of Example 3 and L-glutathione were added to each of the units.
The starting concentrations of the acridine derivative and
L-glutathione were measured and are reported below in Table 1 below
(Time 0). Each unit of packed RBC was transferred to a container,
including the sample membrane (described above). The ratio of
membrane surface to fluid was approximately 2.5 cm.sup.2/ml The
containers were placed on a orbital shaker and agitated at room
temperature. Samples were removed at 1, 4 and 24 hours for
analysis. The packed RBC samples were centrifuged in a microfuge at
maximum RPM and the plasma supernatants were transferred to
separate vials for analysis of L-glutathione (GSH) and acridine
derivative by HPLC. Samples of packed RBCs were also analyzed with
a Sysmex cell counter to determine the degree of hemolysis in the
various samples. The results are summarized in Table 1 below.
1 TABLE 1 Sample Time AD (.mu.M) GSH (mM) % Hemolysis Time 0 584.02
6.75 1.95 1 Hour 124.72 5.77 2.05 4 Hour 6.07 4.88 1.95 24 Hour
1.15 3.85 2.25
[0085] As shown from these examples, a ratio of membrane surface to
fluid of between about 2.0 cm.sup.2/ml -2.5 cm.sup.2/ml is
effective for reducing the concentrations of pathogen inactivating
compounds. Such ratios are particularly effective for the
embodiments shown in FIGS. 1 and 2. (i.e., a membrane sheet within
a container of biological fluid), although any ratios of between
1.0-5.0 cm.sup.2/ml may also be effective for removing pathogen
inactivating compounds in these or other embodiments.
EXAMPLE 4
[0086] The ability of five (5) different membranes, all made in
accordance with the present invention, to remove pathogen
inactivating treating agents from packed red blood cells was also
evaluated. The membranes evaluated included a 70% loading of
activated charcoal in a 10% polyurethane (PNO3) solution (as
defined above). The sample membranes were, in some cases (e.g.,
test articles 2-5), treated with a treating agent and configured
(flat or rippled) as set forth below. For comparison, test article
6 (a control) was a container of packed and treated (as described
below) RBCs that included no sorbent whatsoever.
2TABLE 2: SAMPLE MEMBRANES Test Membrane Article Treatment &
Configuration 1 No treatment & dried, flat 2 0.9% NaCl &
dried, flat 3 0.9% NaCl & dried, rippled 4 0.25% PVOH &
dried, flat 5 0.25% PVOH & dried, rippled 6 No sorbent
(control)
[0087] Seven units of ABO matched whole blood were obtained. Each
unit was centrifuged at 5,000 .times.G for five minutes in a Sorval
RC-3B centrifuge at 4150 rpm. The supernatant plasma was expressed
and 94 ml of a solution that included approximately 25 mM sodium
citrate dihydrate, 4.4 mM sodium acid phosphate dihydrate, 16 mM of
sodium phosphate dihydrate, 1.5 mm adenine and 39.9 mM of mannitol
having a pH of approximately 7.3 was added to each unit. The packed
red blood cells were than pooled in a three liter container. The
measured hematocrit was 64%. The packed RBC were then dispensed
into seven separate containers, each container including
approximately 280 ml of packed red blood cells. The packed red
blood cells were than dispensed into plastic containers and held at
4.degree. C. for approximately four hours.
[0088] Next, the cooled containers were allowed to come to room
temperature. Twenty (20) ml of a 30 mM glutathione solution in 4.1%
dextrose was introduced into a pouch containing approximately 30 mg
of an acridine compound [N,N-bis (2- chloroethyl)] -2-aminoethyl 3
[(Acridinyl-3-yl) amino] proprionate dihydrochloride. The powder
was dissolved and the solution was added to the packed red blood
cells and mixed to obtain final concentrations in the packed red
blood cells of approximately 200 .mu.M of the acridine compound and
2 mM of L-glutathione. After transfer to a secondary container, the
dosed packed red blood cells were held in a static condition at
room temperature for approximately 8 hours.
[0089] Following the 8 hour incubation period, the treated packed
red blood cells were sterile connected to a container including the
membranes made as described above. The containers with packed red
blood cells and the membranes were placed on an orbital shaker (72
cycle/minute) at room temperature for 8 hours. After 8 hours, the
units were transferred to 4.degree. C. storage where they were
agitated once every 4 hours for a 2 minute duration on a platelet
shaker. A sample was collected every 2 hours for the first 8 hours
after transfer to the container including the membrane. Samples
were prepared for HPLC analysis to determine concentrations of the
acridine derivative 5-[(.beta.-carboxyethyl) amino] acridine
(abbreviated as AD) and total L-glutathione (oxidized (GSH) and
reduced (GSSH)). Samples were also analyzed for % hematocrit, %
hemolysis, hemoglobin, ATP concentration, pH and potassium (K+
leakage). Samples were also collected and analyzed after one and
two week exposure to the membrane at 4.degree. C. The results after
8 hours exposure to the membrane are summarized in Table 2 and also
in FIGS. 26-28. The results after 1 week and 2 week exposure to the
membrane are summarized in Tables 4 and 5.
3TABLE 3 SUMMARY OF RESULTS AFTER 8 HOURS EXPOSURE TO MEMBRANE
Residual [ATP] Residual [GSH] and (.mu.mol/g Unit [AD] [GSSH] %
Lysis [K+] Hb) No. Condition (.mu.M) (mM) t = 0 hr t = 8 hr
(mmol/L) % HCT t = 8 hr pH 1 PNO3 Dried, flat 2.45 3.32 0.05 0.26
5.17 67 4.67 6.74 2 PNO3 NaCl, flat 2.89 2.54 0.05 0.29 4.64 63
4.68 6.76 3 PNO3 NaCl, rippled 2.10 2.66 0.06 0.19 4.72 63 4.65
6.77 4 PNO3 PVOH, flat 3.39 2.82 0.04 0.46 5.40 67 4.66 6.75 5 PNO3
PVOH, 2.52 1.80 0.05 0.31 5.22 66 4.68 6.75 rippled 6 Control 54.98
6.13 0.06 0.06 4.77 64 4.64 6.74
[0090]
4TABLE 4 SUMMARY OF RESULTS AFTER 1 WEEK EXPOSURE TO MEMBRANE
Residual Residual [GSH] and [ATP] Unit [AD] [GSSH] [K+] (.mu.mol/g
No. Condition (.mu.M) (mM) % Lysis (mmol/L) % HCT Hb) pH 1 PNO3
Dried, flat 3.99 0.33 0.31 17.10 66 4.35 6.54 2 PNO3 NaCl, flat
3.89 0.35 0.40 15.68 62 4.36 6.55 3 PNO3 NaCl, rippled 2.93 0.46
0.26 15.90 63 4.33 6.53 4 PNO3 PVOH, flat 3.61 0.35 0.52 16.80 65
4.31 6.56 5 PNO3 PVOH, rippled 3.13 0.44 0.42 17.32 65 4.27 6.58 6
Control 70.90 4.12 0.11 16.52 63 4.82 6.49
[0091]
5TABLE 5 SUMMARY OF RESULTS AFTER 2 WEEKS EXPOSURE TO MEMBRANE
Residual Residual [GSH] and [ATP] Unit [AD] [GSSH] [K+] (.mu.mol/g
No. Condition (.mu.M) (mM) % Lysis (mmol/L) % HCT Hb) pH 1 PNO3
Dried, flat 4.08 0.41 0.33 27.83 64 3.48 6.35 2 PNO3 NaCl, flat
4.23 0.39 0.39 24.63 62 3.52 6.35 3 PNO3 NaCl, rippled 3.09 0.50
0.27 25.65 62 3.60 6.35 4 PNO3 PVOH, flat 4.21 0.40 0.50 26.58 63
3.53 6.36 5 PNO3 PVOH, rippled 3.38 0.41 0.39 27.42 65 3.52 6.35 6
Control 80.58 3.94 0.09 26.49 63 3.47 6.33
[0092] As shown from foregoing and in FIG. 26, substantial sorption
of the acridine derivatives was obtained in under 5 hours.
Substantial sorption of L-glutathione (oxidized and reduced) was
also achieved in under 24 hours (FIG. 27). Hemolysis and ATP levels
remained acceptable for transfusion of RBCs to recipients (FIG.
28).
[0093] The present invention has been described, for purposes of
illustration only, in the context of selected embodiments and
methods. It will be appreciated, however, that various
modifications of the embodiments and methods described herein are
possible in accordance with the scope of the appended claims.
* * * * *